Additives for nickel electroplating baths



United States Patent ADDITIVES FOR NICKEL ELECTROPLATING BATHS Wolfgang Giindel, Dusseldorf-Oberkassel, and Wennemar Strauss, Dusseldorf-Holthausen, Germany, assignors to Dehydag, Deutsche Hydrierwerke G. m. b. H., Dusseldorf, Germany, a corporation of Germany No Drawing. Application March 13, 1956 Serial No. 571,125

Claims priority, application Germany March 16, 1955 Claims., (Cl. 204-49) This invention relates to additives for electroplating baths, and more particularly to nickel electroplating baths modified with internal salts of quaternary ammonium-N- alkyl-sulfonic acids.

We have found that high-grade nickel electrodeposits are produced it the customary nickel electroplating bath is modified with internal salts of quaternary ammonium- N-alkyl-sulfonic acids either before or during the electroplating procedure.

The internal salts used as additives for nickel electroplating baths in accordance with the present invention are formed by a reaction of tertiary monocyclic or dicyclic heterocyclic nitrogen compounds of the aromatic type, especially pyridine and its homologues, with lower 1,3- or 1,4-alkylsultones, especially propanesultone and 1,3- or 1,4-butanesultone. The reaction products formed thereby are internal salts of quaternary ammonium-N- propane-w-sulfonic acids or the corresponding butane-wsulfonic acids, depending upon the alkylsultone used, wherein the nitrogen atoms are members of an aromatic ring system. Such compounds may be produced in a very simple manner in accordance with the method described by Helberger in Liebigs Annalen, vol. 565, page 24, by reacting equimolar amounts of the above reactants in the presence of organic solvents or even in an aqueous medium. As a rule, this method produces excellent yields of the reaction product. The internal heterocyclic sulfonates can be readily isolated from the reaction mixture; they crystallize very readily and are very stable under virtually all conditions. When added to nickel electroplating baths, these internal salts effect marked improvement in the brightness and, above all, in the smoothness of the nickel electrodeposits produced from such modified baths.

. The simplest and most readily accessible of these compounds is the internal salt of pyridinium-N-propane-wsulfonic acid having the following structural formula:

which may be obtained, for example, by a reaction of pyridine with 1,3-propancsultone under the conditions set forth by Helberger, supra. However, other analogous internal sulfonic acid salts may also be used in place of the above pyridinium salt, for example those in which the heterocyclic ring system is a C-substituted pyridine radical, such as a picoline, lutidine, ethylpyridine radical, and the like. Similarly, those analogous compounds which contain a polycyclic heterocyclic radical in place of the pyridine or substituted pyridine radical, such as a quinoline, isoquinoline, quinaldine, lepidine, acridine, phenanthridine radical, and the like, may also be used as modifiers of nickel electroplating baths in accordanct with the present invention. Finally, also those interna sulfonic acid salts of the above general class, wherein th pyridine ring is replaced by a heterocyclic radical com prising more than one nitrogen atom in the ring, havt been found to be effective additives for nickel electro plating baths, such as the internal sulfonic acid salts o pyridazine, pyrimidine, pyrazine, phthalazine, quinazo line, quinoxaline, phenazine, and the like. In this las group of compounds the other nitrogen atoms in th heterocyclic ring system may also be linked to additiona internal alkylsulionic acid radicals of the type shown it the structural formula above. Moreover, any of tht heterocyclic radicals recited herein may carry substituent: such as halogen, nitro-groups, and the like.

In addition to 1,3-propanesultone or 1,3- and 1,4 butanesultone, other sultones may be used to produce tht above-described class of additives for nickel electroplating baths. For example, substituted sultones such as 1,1-di methyl-1,3-propanesultone (isopentanesultone) may bl reacted with the various types of heterocyclic compound; above described to produce internal salts of quaternary ammonium-N-dimethyl-propane-w-sulfonic acid. Sucl compounds are also effective additives for nickel electro plating baths and produce the above-mentioned advan tageous effects upon nickel electrodeposits. Finally, in ternal sulfonic acid salts of heterocyclic compounds whicl have been analogously formed from cycloaliphatic sul tones such as tolylsultone, 1,8-naphthalenesultone, and tilt like, may also be used for the purpose herein set forth.

In other Words, we have broadly discovered that com pounds having the general structural formula wherein R is a cyclic radical which includes the nitrogei atom and has carbon atoms or carbon and additiona nitrogen atoms in the ring, and R is a lower aliphatic cycloaliphatic or aromatic radical, are efiective additive for nickel electroplating baths which will produce marked improvement in the brightness and smoothnes of the nickel electrodeposits.

In practice, the compounds herein described are addet to the nickel electroplating bath either as such, that is ii the form of the internal salt, or also in the form of th corresponding metal sulfonates produced by reacting thl internal salt with a suitable inorganic metal base, where by the cyclic sulfonic radical is cleaved to produce tht compound where Me represents the metal atom. The quantity 0 these compounds which is added to the nickel electroplat ing bath to achieve the desired results may range be tween 0.1 and 10 gm. per liter of bath, but amounts be tween 0.4 and 1 gm. per liter of bath are preferred. I1 general, the best results are obtained if the nickel is elec trodeposited from baths modified in accordance with th present invention at a temperature of about 60 C. am at current densities up to about 8 amp./dm.

While nickel electroplating baths modified solely wit] the above compounds will produce the desired improve ment in the nickel electrodeposits, such baths may addi tionally comprise known brighteners, porosity-preventin, agents, Wetting agents and/or salts which increase th conductivity of the bath.

The nickel electroplating baths modified in accordano with our invention may be employed to deposit nickel or 11 types of metals and alloys, for example on iron, alumium, copper, brass and many more; moreover, the comounds may be added to nickel-plating baths employed in ll types of industrial nickehplating processes, including me drum-plating method.

We have found it particularly advantageous to emloy the internal salts described herein in combination ith known brighteners, especially with diarylsulfimides r their salts, such as ditolylsulfimide; when used in this tanner, the smoothness of the nickel electrodeposits is nproved to a remarkable degree, while their ductility :mains unimpaired.

The following examples will further illustrate the resent invention and enable others skilled in the art understand the invention more completely. It must e emphasized, however, that our invention is not limed to the particular compounds mentioned in the exmples.

Example I 0.8 gm. of the inner salt of pyridinium-N-propane-wulfonic acid and from 4 to 8 gm. of the sodium salt of itolyl-disulfimide were added to each liter of a Wattslpe nickel electroplating bath and dissolved therein. Iron nd copper sheet metal were electroplated in this modied bath at a temperature of about 60 C. and an averge current density of 6 amp./dm. The sheet metal as provided with full-bright, ductile nickel deposits, iarked by a high degree of smoothness.

Example II 0.2 gm./l. of the inner salt of the isoquinoliniurn-N- ropane-w-sulfonic acid were used instead of the inner alt of pyridinium-N-propane-w-sulfonic acid of Example A full-bright nickel deposit was obtained.

Example III 0.2 gm./l. of the inner salt of the quinolinium-N- ropane-w-sulfonic acid were used instead of the inner alt of pyridinium-N-propane-w-sulfonic acid of Example A full-bright nickel deposit was obtained.

Example IV 0.5 gm./l. of the inner salt of the Z-methyl-pyridiniuml-butane-w-sulfonic acid were used instead of the inner alt of pyridinium-N-propane-w-sulfonic acid of Example A full-bright nickel deposit was obtained.

Example V 0.4 gm./l. of the inner salt of the 2,4-dimethyl-pyriinium-N-propane-w-sulfonic acid were used instead of ie inner salt of pyridinium-N-propane-w-sulfonic acid f Example I. A full-bright nickel deposit was obtained.

Example VI 0.1 gm./l. of the inner salt of the 3-bromo-pyridiniumi-propane-w-sulfonic acid were used instead of the inner ilt of pyridinium-N-propane-w-sulfonic acid of Example A full-bright nickel deposit was obtained.

Example VII 0.05 gm./l. of the inner salt of the acridinium-N-proane-w-sulfonic acid were used instead of the inner salt E pyridinium-N-propane-w-sulfonic acid of Example I. full-bright nickel deposit was obtained.

Example VIII 0.15 gm./l. of the inner salt of the pyrazinium-N- utane-w-snlfonic acid were used instead of the inner llt of pyridinium-N-propane-w-sulfonic acid of Exnple I. A full-bright nickel deposit was obtained.

Example IX 6 gm./l. of the sodium salt of di-p-tolyl di-sulfimide ere substituted for the sodium salt of ditolyl disulmide. A full-bright nickel deposit was obtained.

Example X 8 gm./l. of the sodium salt of di-o-tolyl disulfimide were substituted for the sodium salt of ditolyl disulfimide. A full-bright nickel deposit was obtained.

Example X I 6 gm./l. of the sodium salt of dibenzene disulfimide were substituted for the sodium salt of ditolyl disulfimide. A full-bright nickel deposit was obtained.

While we have illustrated the general principle of our invention by a specific embodiment, it will be apparent to persons skilled in the art that the invention is not limited thereto, and that various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. An acid Watts-type nickel electroplating bath having dissolved therein a heterocyclic compound having the general structural formula selected from the group consisting of and RiSO- Me R\ wherein R N is a heterocyclic radical, R being a cyclic radical with 0 to 1 ring nitrogen atoms, the remainder being carbon atoms, and R is selected from the group consisting of lower aliphatic, cycloaliphatic and aromatic radicals, and Me is an alkali metal atom, said compound being present in an amount sufiicient to produce smooth and ductile nickel electrodeposits.

2. An acid Watts-type nickel electroplating bath having dissolved therein about 0.ll0 grams per liter of an internal salt of pyridinium-N-alkylsulfonic acid having the structural formula wherein R is a lower alkyl radical having from 3 to 4 carbon atoms.

3. An acid Watts-type nickel electroplating bath having dissolved therein about 0.1-l0 grams per liter of the internal salt of pyridinium-N-propane-w-sulfonic acid.

4. An acid Watts-type nickel electroplating bath as in claim 3, comprising in addition from about 4 to 8 grams per liter of a compound selected from the group consisting of diarylsulfimides and their water-soluble salts.

5. An acid Watts-type nickel electroplating bath as in claim 3, comprising in addition from about 4 to 8 grams per liter of the sodium salt of ditolyl-disulfimide.

6. The method of producing bright and smooth nickel electrodeposits on metal objects, which comprises electroplating said objects in an acid Watts-type nickel bath having dissolved therein a heterocyclic compound having the general structural formula selected from the group consisting of is a heterocyclic radical, R being a cyclic radical with 0 to 1 ring nitrogen atoms, the remainder being carbon atoms, and R is selected from the group consisting of lower aliphatic, cycloaliphatic and aromatic radicals, and Me is an alkali metal atom, said compound being present in an amount sufficient to produce smooth and ductile nickel electrodeposits.

7. The method of producing bright and smooth nickel electrodeposits on metal objects, which comprises electroplating said objects in an acid Watts-type nickel bath having dissolved therein about 0.1- grams per liter of an internal salt of pyridinium-N alkylsulfonic acid having the structural formula its wherein R, is a lower alkyl radical having from 3 to 4 carbon atoms.

8. The method of producing bright and smooth nickel electrodeposits on metal objects, which comprises electroplating said objects in an acid Watts-type nickel bath having dissolved therein about 0.1-10 grams per liter of the internal salt of pyridinium-N-propane-w-sulfonic acid.

9. The method of producing bright and smooth nickel electrodeposits on metal objects, which comprises electroplating said objects in an acid Watts-type nickel bath having dissolved therein about 0.1-10 grams per liter of the internal salt of pyridinium-N-propane-w-sulfonic acid and from about 4 to 8 grams per liter of a compound selected from the group consisting of diarylsulfimides and their water-soluble salts.

10. The method of producing bright and smooth nickel electrodeposits on metal objects, which comprises elec' troplating said objects in an acid Watts-type nickel bath having dissolved therein about 0.11() grams per liter of the internal salt of pyridinium-N-propane-w-sulfonic acid and from about 4 to 8 grams per liter of the sodium salt of ditolyl-sulfimide.

References Cited in the file of this patent UNITED STATES PATENTS 2,469,727 Hoffman May 10, 1949 2,647,866 Brown Aug. 4, 1953 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Noe 3:) Wolfgang (ffindel et a1.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 52, for "R SO Me" read m R sonne ==3 column A, line 27, for "R SO Me" reed R SO Me column 5, line 2, for "R so me read R SO M Signed and sealed this 13th day of October 1959,

(SEAL) Attest:

KARL YAXLINE ROBERT c. WATSON Attesting Oflicer Commissioner of Patents 

1. AN ACID WATTS-TYPE NICKLE ELECTROPLANTING BATH HAVING DISSOLVED THERIN A HETEROCYCLIC COMPOUND HAVING THE GENERAL STRUCTURAL FORMULA SELECTED FROM THE GROUP CONSISTING OF 